Consequences of refuge for the functional response of Dermestes ater (Coleoptera: Dermestidae) to Musca domestica (Diptera: Muscidae)

Dermestes (s.str.) haemorrhoidalis (Coleoptera: Dermestidae)-The Most Frequent Species on Mummified Human Corpses in Indoor Conditions? Three Cases from Southwestern Poland

Beetles of the family Dermestidae, especially of the genus Dermestes Linnaeus, 1758, are often identified on corpses in late stages of decomposition. They usually feed on remains devoid of organs and soft tissues or when the corpses undergo mummification. In Europe, eight species from two subgenera Dermestes and Dermestinus Zhantiev, 1967, have so far been identified on human corpses. Despite the relatively frequent presence of Dermestes sp. in experimental studies conducted in Poland, no reports concerning Dermestes directly collected from human corpses have been published to date. This article again describes observations of Dermestidae collected from human corpses found in indoor conditions in Wrocław, the capital of the Dolnośląskie Voivodeship. For the second time, there is evidence of the presence of Dermestes (s.str.) haemorrhoidalis on human corpses-a species considered to be relatively rare, as evidenced by faunistic data published from Poland, as well as the results of ongoing experiments of forensic interest.

Experimental Evidence of Bone Lesions Due to Larder Beetle Dermestes maculatus (Coleoptera: Dermestidae)

Simple Summary

Larvae of the larder beetle Dermestes maculatus (Coleoptera: Dermestidae, De Geer, 1774) resemble caterpillars but actually feed on dry tissues of dead animals, and sometimes on human corpses. To hide and metamorphose into adult beetles, these larvae dig deep tunnels called pupation chambers. These holes and pits are usually observed in skins, horns, furs, or surrounding materials such as wood. They have also been reported on archaeological bones and experimentally observed on fresh pig bones, but never on humans. In this context, we investigated whether larder beetle larvae could also dig pupation chambers in human bones, and under which conditions this could occur. For this purpose, we placed medieval dry human bones as well as fresh calf and beef bones (control) with Dermestes maculatus larvae. After 1 month, we observed tunnels corresponding to pupation chambers only on dry human bones, and under conditions of high larval density. Despite these results being preliminary, they are, nonetheless, of particular interest in a forensic context, as they could help to understand taphonomic bone modifications or even the chronology of mass grave deposals.

Abstract

Dermestid beetles (Coleoptera: Dermestidae) are necrophagous insects feeding on mummified carcasses. After six to seven molts, the larvae stop feeding and dig pupation chambers to hide and safely evolve into adults. Such pupation chambers have already been observed on archaeological mammals’ bones, but the attribution and interpretation of these osteological lesions lack experimental evidence in a forensic context. To observe whether dermestid larvae dig pupation chambers in human bones, 20 or 40 Dermestes maculatus (De Geer, 1774) larvae were placed in a dermestarium with different types of bones varying in species (Bos taurus or human), age (adult or immature), and preservation method (fresh or dry). Our results show that dermestid larvae caused multiple lesions, including larval mandible traces on cortical bone, cortical perforations, drilling of pupation chambers, destruction of the trabecular network, and the perforation of cartilage. Bone destruction was mainly observed on aged dry bones, while fresh bones only exhibited soft tissue and superficial cartilage lesions. According to these results, pupation chambers could indicate the simultaneous presence of several corpses at different decomposition stages, or the addition of new corpses while others were already skeletonized. These conclusions are particularly important in the case of mass graves, where chronology is sometimes difficult to establish.

A mummified human corpse and associated insects of forensic importance in indoor conditions

We report, for the first time from Poland, the presence of Dermestes haemorrhoidalis (Coleoptera: Dermestidae) on a mummified human corpse found in a flat (Lower Silesia province, south-western Poland). Different life stages of D. haemorrhoidalis were gathered from the cadaver, and the signs of activity of these beetles (i.e. frass) were observed. On the basis of these facts, we concluded that the decedent, whose remains were discovered in the flat on 13 December 2018, died no later than the summer of 2018, with a strong probability that death occurred even earlier (2016 or 2017). A case history, autopsy findings, and entomological observations are provided. The presence of larvae of Dermestidae in the empty puparia of flies is reported for the first time. A list of the invertebrate species found in the corpse is provided, compared with available data, and briefly discussed.

A Biological and Procedural Review of Forensically Significant Dermestes Species (Coleoptera: Dermestidae)

The analyses of the insect species found on decomposing remains may provide useful information for the estimation of the minimum time elapsed since death and other parameters, such as causes and circumstances of death. The majority of research has focused on the early colonizing species, typically blowflies, while research concerning late colonizing insects is currently sparse. Dermestid beetles of the genus Dermestes L. (Coleoptera: Dermestidae) are one of the predominant insect species associated with decomposing remains during dry decay and skeletal stages of decomposition. In some dry environments, Dermestes species are likely to be the only necrophagous insects feeding on the decomposing remains. Furthermore, Dermestes species (immature and adults), their remains (cast skins and fecal material), and their artifacts (pupal chambers) are frequently found associated with ancient remains (e.g., mummies, fossils). Dermestes species have a worldwide distribution and are considered important in decomposition processes, forensic investigations, and economically as a known pest of stored products. Despite their recognized forensic importance, there is limited data documenting the ecology, biology, and the growth rates of the forensically relevant species. The aim of this review is to provide a comprehensive synopsis on the available literature concerning Dermestes species associated with forensic cases. In particular, aspects of colonization behavior, growth rates for forensic taxa and potential best practice guidelines for forensic casework encompassing late colonizing Dermestes species are discussed.

Involvement of larder beetles (Coleoptera: Dermestidae) on human cadavers: a review of 81 forensic cases

From 1994 to 2013, French forensic entomology laboratories investigated 1,093 cases. Larder beetles (Coleoptera: Dermestidae) were observed in 81 (7.5%) of these cases. To describe and analyze these 81 cases, eight parameters were used: city, location (indoor or outdoor), decay stage (fresh, decay, or dry), dermestid species and instar (adults and/or larvae), presence of living calliphorid larvae, presence of calliphorid pupae or adults, and presence of other necrophagous species. Eight Dermestidae species were observed: Dermestes frischii (42% of cases), Dermestes undulatus (35.8%), Dermestes peruvianus (12.3%), Dermestes lardarius (9.9%), Dermestes haemorrhoidalis (8.6%), Dermestes maculatus (7.4%), Dermestes bicolor (3.7%), and Dermestes ater (1.2%). Larder beetles primarily developed on human cadavers in outdoor locations in areas with a dry climate and were never reported in oceanic areas (which are characterized by frequent rainfall and high ambient humidity). The number of dermestid species on a single corpse never exceeded three. Typically, one species was found per corpse. Species differed between indoor and outdoor cases, with D. frischii and D. undulatus dominant in outdoor cases, while D. peruvianus dominant in indoor cases. Calliphoridae was found in 88% of the cases, while Hydrotaea and Piophilidae were observed 40% of the time. Regarding Coleoptera, Necrobia spp. (Coleoptera: Cleridae) was observed in 46% of the cases. Lastly, we observed a typical decomposition pattern, with preferential feeding areas on the face, hands, and feet (i.e., the extremities). Pupation chambers on or inside the bones were not observed.